Jet drilling fishing bit

ABSTRACT

A hydraulic jet drill bit has a single large flute extending the full length of the bit. A junk basket open at its top is mounted on the top of the drill bit. The junk basket has the same shape in plan view as the drill bit to provide a continuation of the flute through the junk basket. An adapter of small diameter extends upward through and above the junk basket for connection to drill pipe. When recovering junk from the hole, junk is washed into the flute by circulating drilling liquid while the bit is held just off bottom. After circulating for a short time, the bit is lowered onto the bottom while circulation of drilling liquid continues to drill the hole and thereby indicate recovery of the junk.

,384,192 5/1968 Goodwin et a1.. 3,414,070 12/1968 Pekarek.......................,

Primary Examiner-David H. Brown Attorneys-Meyer Neishloss, Deane E. Keith and Pau1 L.

r1`lls0n a B 9 5 9 H 1 1 7 2 2, 2 l 9, 2

Horst H. Hasiba Ptsbnrgh, Pa. 864,590 Filed 0m. 8, 1969 [45] Patented Apr. 27, 1971 Gulf Reh @i Development Company Pittsburgh, Pa.

[72] Inventor [21] Appl. No.

[73] Assignee [54] J ET DWULLWG IFIIS al] 175/400X and thereby indicate recovery of the junk.

5/1955 Freeman et al.

PATENTEU me? |971 SHEEY l UF 3 INVENTOR. HORST H. HAS/BA PATENTEU m27 m1 SHEET 2 0F 3 INVENTOR. HORST H. HA

S/BA

This invention relates to the drilling of wells and more particularly to a method and apparatus for removal of junk from the borehole of a well,

During the drilling of a well pieces of steel, usually referred to as junk are sometimes inadvertently dropped down the borehole of the well. For example, in rotary drilling with the conventional cone-type drill bits, the cone of the drill bit may break loose from the bit and be left in the well. The junk must be removed from the borehole before drilling can proceed.

One method of drilling that has been developed for drilling hard formations is hydraulic jet drilling. In that method highvelocity streams of' an abrasive-laden liquid are discharged against the bottom of the borehole to penetrate the rock. Because of the extremely erosive conditions at the bottom of the borehole, parts of the drill bit used in hydraulic jet drilling are made of tungsten carbide. lf those parts are broken from the bit and le in the borehole, drilling must stop until the tungsten carbide piece is removed from the hole. Because of the hardness of tungsten carbide, it cannot be broken up, and the extremely high density of tungsten carbide makes removal of such particles from the hole difficult.

A number of tools have been developed for the recovery of junk from the hole. One of the shortcomings of most tools has been the absence of any means for determining whether or not all of the junk has been recovered. lf it cannot be detemtined whether or not all of the junk has been recovered before the tool is removed from the hole, the expense and loss of time of an additional round trip into the hole with the junk recovery equipment may incurred. The problem is aggravated in jetdrilling operations because the hard fonnations in which jet drilling is most effective are ordinarily at substantial depths and round trips at those depths result in greater loss of time.

This invention resides in a jet-fishing bit adopted to be attached to the lower end of drill pipe and a method for recovering junk in a single trip into the well. The bit comprises a cylindrical bit body closed at its lower end having a plurality of nozzles extending through the bottom of the drill bit for the discharge of drilling liquid from the bit against the bottom of the borehole. A flute large enough to permit the passage of the largest pieces of junk likely to be encountered extends longitudinally from the bottom to the top of the drill bit. A junk basket of substantially the same horizontal crosssectional configuration as the bit body and open at the bit to catch junk which settles from the drilling liquid as the velocity of the drilling liquid decreases above the junk basket. Drilling liquid is discharged at a high velocity through the nozzles in the bit to wash junk up through the flute into the basket. Circulation of drilling liquid is continued to deepen the hole.

ln the drawings:

FIG. l is a perspective view of the fishing bit of this invention.

FIG. 2 is a plan view of the bottom ofthe fishing bit.

FlG. 3 is a longitudinal sectional view taken along section line Ill-lll in FlG. 2.

FIG. @l is a horizontal sectional view taken along section line lV-IV in FIG. 3.

FIG. 5 is a horizontal sectional view taken along section line V-V in FIG. l.

Referring to FIG. l, the fishing bit indicated generally by reference numeral l0 is illustrated with a drill bit constituting the lower part of the fishing bit made up of a bit body l2- and a bit top ld welded to the upper end of the body l2. An upwardly opening junk basket lo is mounted on the upper end of top ld. Junk basket l@ is perforated as indicated at 18 to permit drainage of the drilling liquid as hereinafter described. Extending upwardly through the junk basket i6 in an offcenter position is a neck 22 of top M for connection to the lower end of an adapter indicated generally by reference numeral 20. Adapter is composed of an upper vertical section 2li for connection to the lower end of drill pipe 26 and an angled section 27 connecting the centrally positioned upper section 2d with the offcenter neck 22. The bit body l2, top le and junk basket 16 have a cross-sectional shape in the form of a sector larger than 180 of a circle with a large flute 23 extending longitudinally from the bottom of the bit to the top of the junk basket. Referring to FIG. 2 in which the bottom of the bit is shown in plan, the flute 28 is in the fonn of a sector which has been found to be large enough to allow passage of the largest pieces of junk most likely to be dropped in the hole from a jet drill bit. Flute 28 extends substantially all of the way inward to the center of rotation of the bit to provide an opening having a shape allowing junk with large dimensions in more than one plane to pass. lt is preferred that the flute occupy a sector of 75 to 120. In jet drilling the largest pieces are most likely to be backsplash plates of tungsten carbide attached to the bottom of the drill bit used in jet drilling.

Bit body 12 is closed at its lower end. Extending through the bottom of the bit with their outlets flush with the lower surface of the bit are a plurality of nozzles 30 for the discharge of jet streams of drilling liquid. To minimize wear by the highvelocity stream of abrasive-laden liquid passing through the nozzles, nozzles 30 are constructed of an abrasion-resistant material such as tungsten carbide alloys. Nozzles 30 are positioned and oriented in the drill bit whereby upon rotation of the drill bit the jet streams discharged from the nozzles will cut into the borehole over the full diameter of the borehole. In accordance with the usual consideration in designing drill bits for hydraulic jet drilling, more nozzles are placed near the periphery than near the center of rotation of the bit because of the longer distance a nozzle travels in a single revolution of the bit and the larger amount of rock that must be removed at the larger radial distances. lt is desirable that the jet streams cut grooves of substantially uniform depth over the full diameter of the borehole. lt is contemplated that the jet streams will cut a central hole and a plurality of concentric grooves separated by thin, easily broken, ridges.

The nomles 30 extend upwardly through the bottom of the drill bit into a cavity 32, indicated by broken lines in FIG. 2, in body l2. ln a preferred form of the fishing bit of this invention, the bit body l2 consists of a single piece of steel in which cavity 32 is cut. A reinforcing web 34 extends across the lower surface of cavity 32.

Extending downwardly from the lower surface of the body l2 are a plurality of standoff elements 36. The standoff elements 36 illustrated are conical in shape and taper downwardly to extend partially into grooves cut by the jet streams discharged from some of the nozzles and ride on ridges forming walls of the grooves. Standoff elements 36 fix the distance between the bottom of the borehole and the nozzle outlets which are flush with the lower surface of the body l2. Also extending downwardly from the lower surface of the body ll2 is a plow 38. Plow 38 extends downwardly a distance designed to cause the plow to ride just above the bottom of the borehole and push junk into the flute 28. A portion 40 of the lateral surface of the body l2 opposite flute 28 is hard surfaced t0 prevent excessive wear resulting from the net force of the drilling liquid in the flute 23 pushing the bit toward the vborehole wall. Other parts of the bit, such as the bottom and lateral surfaces of plow 38, are also hard surfaced to reduce wear.

A central hole 42 extends downwardly through a cover member lo closing the top 14 ofthe bit and thereby provides a continuation of the passage through the neck 22 to deliver drilling liquid into the bit. A cavity M in the top 14 of the bit matches the corresponding cavity 32 in the body l2 and forms a chamber into which the drilling liquid delivered through neck 22 flows and from which the drilling liquid is delivered to the inlet end of the nozzles 30. Cavity del is indicated by dotted lines in FIG. 3. Top ld can conveniently be manufactured by machining cavity M and drilling passage l2 in a block of metal having the desired external shape. The sidewalls, cover member and bottom of the bit are of heavy construction to withstand the high pressure of the drilling liquid used in jet drilling.

Junk basket 16 mounted on the upper end of the top 14 has the same horizontal cross-sectional shape as the bit. The walls 47 of the junk basket can be of relatively light weight metal because they do not have to withstand the high-pressure differentials that exist between the cavities 32 and 44 and the outside of the bit. Adapter 20 is welded to the upper end of the neck 22 and provides a passage for the delivery of drilling liquid from the drill pipe into the drill bit. Adapter 20 has a small diameter relative to the diameter of the bit to leave a large annular space immediately above the junk basket. The diameter of adapter 20 is preferably 40 percent to 60 percent of the diameter of the bit body.

ln the design of the jet-diilling fishing bit of this invention, it is essential that the flute have a cross-sectional area large enough to allow the largest pieces of tungsten carbide likely to be broken from a jet-drilling bit to be lifted by the upwardly flowing drilling liquid and dropped into the junk basket. The area of the flute 20 must be correlated with the number of noules 30 and their internal diameter to provide an upward flow rate through the flute 20 capable of lifting the junk. For example, a fishing bit 9 inches in diameter having a flute occupying a sector of 90 and having 20 nozzles of 0.17 inch diameter has been found capable of removing tungsten carbide junk including pieces ranging up to l lb. l oz. in weight with a drilling liquid having a density of l2 lbs/gal. at a flow rate of 520 gals/min. Calculations indicate that if the flow rate is increased to 900 gals/min., individual pieces of tungsten carbide weighting as much as l0 lbs. can be lifted and retrieved. The exact discharge velocity for a given pressure drop through the nozzle will depend on the density of the drilling liquid. For a given pressure drop through the nozzles, the discharge velocity of the drilling liquid decreases as the density of the drilling liquid is increased. A drilling liquid suitable for hydraulic jet drilling such as an aqueous suspension of clay solids and plant fibers in a concentration adequate to suspend l to l0 percent by volume steel shot can be used in the fishing operation.

lt is essential to the fishing bit of this invention that, in addition to supplying the desired flow rate upwardly through the flute, the velocity of drilling liquid discharged from the nozzles be high enough to cause drilling at a rate high enough to allow detennination in a reasonable time of whether the junk has been recovered. A velocity of at least about 500 feet/second is desirable. A pressure drop of 4,000 p.s.i. through the nozzles gives a discharge velocity from the nozzles higher than 500 feet per second. Since hydraulic jet drilling requires jet streams from the nozzles to strike the bottom of the borehole at intervals over the full diameter of the borehole, a plurality of' nozzles is required. The diameter of the nozzles should be in the range of about three thirtyseconds to three-eighths inch to allow the desired high nozzledischarge velocities to be obtained without requiring such high volumetric flows that pressure drop through the drill pipe would be excessive.

ln the operation of the fishing bit of this invention, the fishing bit is attached to the lower end of drill pipe and lowered into the borehole until a few inches above the bottom of the borehole. Circulation of drilling liquid is commenced at a rate such that the pressure drop through the nozzles is at least 4,000 p.s.i. and the fishing bit lowered onto the junk in the hole. The fishing bit is then backed off while circulation is continued to wash the junk into the flute, then the bit is slowly lowered while circulation is continued. The relatively large horizontal cross-sectional area of the fishing bit causes a high velocity through the flute. As the drilling liquid flows past the top of the junk basket into the enlarged annular space surrounding adapter 20, its velocity decreases sharply and junk is dropped from the drilling liquid into the basket. Holes 18 in the junk basket allow drilling liquid to escape from the junk basket and thereby facilitate settling of junk into the basket.

After circulation of drilling liquid for a short time, for example, l0 minutes, the bit is rotated while drilling liquid is circulated. A light weight, such as 1,000 lbs., is applied to the bit while it is rotated and downward movement of the d rill pipe observed to see whether or not the borehole is being deepened. After drilling a short distance such as 5 or l0 feet to show that the hole has been cleared, the fishing bit is pulled from the hole and replaced with a hydraulic jet drill bit and regular drilling is resumed. The ability to observe whether or not drilling can be accomplished insures the removal of the junk from the bottom of the hole before the bit is pulled from the hole, and thereby avoids the possibility of leaving junk in the hole and requiring another trip into the well with the fishing bit.

lclaim:

l. A tool for the recovery of junk from a well comprising a tubular bit body closed at its lower end and adapted to be connected to the lower end of drill pipe, a plurality of nozzles extending through the lower end of the bit body, the number and location of the nozzles being adapted to discharge jet streams against the bottom of the borehole of the well at intervals over the full diameter of the borehole on rotation of the tool, an upwardly opening junk basket mounted on top of the bit body, and a flute extending longitudinally the full length of the bit body and the junk basket.

` 2. A tool as set forth in claim l having an overall circular shape in horizontal section, and in which the flute occupies a sector of 75 to 120.

3. A tool as set forth in claim l in which the flute is in the shape of a sector of 75 to 120 and extends radially inward substantially to the center of rotation of the drill bit body.

4. A tool as set forth in claim l in which the outlets of the nozzles are substantially in the plane of the lower surface of the bottom of the bit, and standoff elements extend downwardly from the lower surface of the bottom of the bit for engagement with the bottom of the borehole to fix the distance of the outlets of the nozzles from the bottom of the borehole.

5. A tool as set forth in claim 4 in which the standoff elements are conical and have their apexes extending downwardly, and thel standoff elements are positioned to extend partially into grooves cut in the bottom of the borehole by jet streams discharged from the nozzles.

6. A tool as set forth in claim l in which a plow member extends downwardly from the bottom of the bit body on the edge moving toward the flute as the bit rotates.

7. A tool as set forth in claim l in which a neck extends from the bit upwardly in an olcenter position through the junk basket, an adapter connected to the lower end of the drill pipe extends downwardly at an angle and is connected to the upper end of the neck, and the cross section of the adapter is in the range of 40 to 60 percent of the area of the borehole.

A tool for the recovery of junk from a well comprising a cylindrical bit body having a substantially flat bottom, nozzles extending through the bottom of the bit body having outlets flush with the lower surface of the bottom of the bit body, said nozzles being located and oriented to discharge jet streams against the bottom of the borehole at intervals over substantially the full diameter of the borehole as the tool is rotated, standoff elements extending downwardly from the lower surface of the bottom of the bit for engagement with the bottom of the borehole to fix the distance from the nozzle outlets to the bottom of the borehole, a junk basket mounted on the upper end of the cylindrical bit body, a flute occupying an approximately sector extending the full length of the cylindrical bit body and the junk basket, a plow extending downwardly from the lower surface of the bottom of the bit along the edge moving toward the flute on rotation of the bit, a neck extending upwardly in an offcenter position from the bit body, and an adapter extending from the upper end of the neck for connection to drill pipe, said adapter having a crosssectional area less than about 60 percent of the cross-sectional area of the borehole. 

1. A tool for the recovery of junk from a well comprising a tubular bit body closed at its lower end and adapted to be connected to the lower end of drill pipe, a plurality of nozzles extending through the lower end of the bit body, the number and location of the nozzles being adapted to discharge jet streams against the bottom of the borehole of the well at intervals over the full diameter of the borehole on rotation of the tool, an upwardly opening junk basket mounted on top of the bit body, and a flute extending longitudinally the full length of the bit body and the junk basket.
 2. A tool as set forth in claim 1 having an overall circular shape in horizontal section, and in which the flute occupies a sector of 75* to 120*.
 3. A tool as set forth in claim 1 in which the flute is in the shape of a sector of 75* to 120* and extends radially inward substantially to the centeR of rotation of the drill bit body.
 4. A tool as set forth in claim 1 in which the outlets of the nozzles are substantially in the plane of the lower surface of the bottom of the bit, and standoff elements extend downwardly from the lower surface of the bottom of the bit for engagement with the bottom of the borehole to fix the distance of the outlets of the nozzles from the bottom of the borehole.
 5. A tool as set forth in claim 4 in which the standoff elements are conical and have their apexes extending downwardly, and the standoff elements are positioned to extend partially into grooves cut in the bottom of the borehole by jet streams discharged from the nozzles.
 6. A tool as set forth in claim 1 in which a plow member extends downwardly from the bottom of the bit body on the edge moving toward the flute as the bit rotates.
 7. A tool as set forth in claim 1 in which a neck extends from the bit upwardly in an offcenter position through the junk basket, an adapter connected to the lower end of the drill pipe extends downwardly at an angle and is connected to the upper end of the neck, and the cross section of the adapter is in the range of 40 to 60 percent of the area of the borehole.
 8. A tool for the recovery of junk from a well comprising a cylindrical bit body having a substantially flat bottom, nozzles extending through the bottom of the bit body having outlets flush with the lower surface of the bottom of the bit body, said nozzles being located and oriented to discharge jet streams against the bottom of the borehole at intervals over substantially the full diameter of the borehole as the tool is rotated, standoff elements extending downwardly from the lower surface of the bottom of the bit for engagement with the bottom of the borehole to fix the distance from the nozzle outlets to the bottom of the borehole, a junk basket mounted on the upper end of the cylindrical bit body, a flute occupying an approximately 90* sector extending the full length of the cylindrical bit body and the junk basket, a plow extending downwardly from the lower surface of the bottom of the bit along the edge moving toward the flute on rotation of the bit, a neck extending upwardly in an offcenter position from the bit body, and an adapter extending from the upper end of the neck for connection to drill pipe, said adapter having a cross-sectional area less than about 60 percent of the cross-sectional area of the borehole. 